Content reproducing apparatus, audio reproducing apparatus and content reproducing method

ABSTRACT

A content reproducing apparatus is disclosed which includes: a sensor; a discrimination circuit configured to discriminate whether a movement of a user is a first movement or a second movement based on a detection output from the sensor; a storage configured to store contents; a reproduction circuit configured to reproduce the contents; and a control circuit configured to supply the reproduction circuit with contents retrieved from the storage in accordance with a discrimination output from the discrimination circuit.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2006-040052 filed in the Japanese Patent Office on Feb.17, 2006, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a content reproducing apparatus, anaudio reproducing apparatus, and a content reproducing method.

2. Description of the Related Art

In recent years, growing numbers of people, increasingly conscious oftheir health conditions, have come to take up walking, jogging, orrunning as a preferred way to maintain and improve their health or staygenerally in shape. To obtain a certain level of salutary effects fromsuch activities usually demands the people to spend suitably prolongedperiods of time on their athletic pursuit.

There have been proposed a number of audio reproducing apparatusesdesigned to support people in walking or running. Some of the proposedapparatuses are disclosed illustratively in Japanese Patent Laid-OpenNos. 2001-299980, 2003-177749, and 2005-156641. One such apparatus isstructured to be easy to carry by a user and stores songs of variabletempos. When the user takes a walk, for example, the apparatus detectsthe tempo of the walking and lets the user listen to songs of the tempofit for the detected pace of walking. The tempo of walking isrepresented illustratively by the number of steps per unit time (e.g.,per minute) and the tempo of songs by the number of beats per minute.

For example, if the walking tempo is 120 bpm (beats per minute), thenthe apparatus reproduces songs at a tempo of 120 bpm, such as marches.This type of audio reproducing apparatus allows the user to walkrhythmically in keeping with the tempo of the songs being played. Theapparatus is thus supposed to afford the user a pleasing walkingexperience.

In this specification, the terms “walking” and “running” will be usedseparately only if these two activities need to be distinguished fromeach other. If there is no specific need to separate these activities,they may be simply referred to as walking or walk/run.

SUMMARY OF THE INVENTION

Walking-support audio reproducing apparatuses of the above-outlined typegenerally utilize acceleration sensors to detect the user's bodilymovements in terms of acceleration. The acceleration thus detected andoutput by the sensor is analyzed so as to determine the tempo of theuser's walking.

FIGS. 11A and 11B show typical waveforms derived from a detection outputfrom an acceleration sensor. FIG. 11A gives a waveform of a user duringwalking, and FIG. 11B illustrates a waveform of the same user duringrunning. In both cases, the waveforms were acquired by a walking-supportaudio reproducing apparatus hung by a neck strap from the neck of theuser who was walking or running. In FIGS. 11A and 11B, the horizontalaxis stands for time and the vertical axis for the output voltage (inmV) from the acceleration sensor.

In these waveforms, the peaks indicated with small circles representchanges in acceleration caused by the impact of the user's foot hittingthe ground. The periodicity of these peaks thus corresponds to the tempoof walking. The peaks with no circles attached stand for changes inacceleration caused by the audio reproducing apparatus swaying by itselfor hitting the user's body during swing motion. As such, the latterpeaks may be regarded as noise. With these characteristics taken intoconsideration, analyses of the waveforms in FIGS. 11A and 11B derivedfrom the detection output from the sensor should permit detection of theuser's walking tempo.

In practice, however, most apparatuses of the above type do not takeinto account the noise experienced in analyzing the walking tempo basedon the detection output as shown in FIGS. 11A and 11B. In the waveformsof FIGS. 11A and 11B, a noise-incurred peak detected near a midpointbetween two adjacent circle-marked peaks representative of the walkingtempo can be interpreted erroneously as another peak attributable towalking. Because such false measurements are apparently consistent withthe walking-triggered peak pattern, the audio reproducing apparatusoften leaves the error uncorrected. In addition, unlike in normal timesthe audio reproducing apparatus often has difficulty in correctlyperforming spectrum analysis and autocorrelation calculations of theuser's movements during transient times. In such cases, the tempodetected from walking can take on a highly unlikely value.

The present invention has been made in view of the above circumstancesand provides arrangements for overcoming the above and otherdeficiencies of the related art.

In carrying out the invention and according to one embodiment thereof,there is provided a content reproducing apparatus including: a sensor; adiscrimination circuit configured to discriminate whether a movement ofa user is a first movement or a second movement based on a detectionoutput from the sensor; a storage configured to store contents; areproduction circuit configured to reproduce the contents; and a controlcircuit configured to supply the reproduction circuit with contentsretrieved from the storage in accordance with a discrimination outputfrom the discrimination circuit.

Preferably, the content reproducing apparatus may further include ananalysis circuit configured to analyze tempos of the first movement orthe second movement of the user in accordance with the detection outputfrom the sensor. The analysis circuit may change analysis algorithms foranalyzing the tempos based on the discrimination output from thediscrimination circuit and the control circuit may retrieve contentsfrom the storage in accordance with the tempo analyzed by the analysiscircuit.

Preferably, the first movement and the second movement of the user maybe walking and running respectively.

According to another embodiment of the present invention, there isprovided a content reproducing method including the steps of:discriminating whether a movement of a user is a first movement or asecond movement based on a detection output from a sensor; and supplyinga reproduction circuit with contents retrieved from a storage storingthe contents in accordance with a discrimination output from thediscriminating step.

According to a further embodiment of the present invention, there isprovided a storage medium which stores a computer-readable program forcausing a computer to execute a procedure including the steps of:discriminating whether a movement of a user is a first movement or asecond movement based on a detection output from a sensor; and supplyinga reproduction circuit with contents retrieved from a storage storingthe contents in accordance with a discrimination output from thediscriminating step.

According to an embodiment of the present invention, as outlined above,the analysis algorithms in use are changed between walking and running.That means an optimal algorithm can be selected to analyze the tempos ofwalking or running. The selective algorithm usage translates intoappreciably fewer errors in the result of the analysis than before.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram showing how an embodiment of thepresent invention is structured;

FIG. 2 is a tabular view explanatory of the present invention;

FIG. 3 is a schematic view of lists explanatory of the presentinvention;

FIG. 4 is a schematic flow diagram showing part of the embodiment of thepresent invention;

FIG. 5 is a graphic representation explanatory of the present invention;

FIG. 6 is another graphic representation explanatory of the presentinvention;

FIG. 7 is a schematic view with tables explanatory of the presentinvention;

FIG. 8 is another graphic representation explanatory of the presentinvention;

FIGS. 9A and 9B are tabular views explanatory of the present invention;

FIG. 10 is a diagrammatic view explanatory of the present invention; and

FIGS. 11A and 11B are waveform charts explanatory of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Overview of thePresent Invention

In the past, analyzing the detection output from the acceleration sensoroften led to errors as mentioned above. That was because the tempos ofthe user's walk/run were obtained using the same analysis algorithmregardless of the difference between walking and running in terms ofwaveforms derived from the acceleration sensor detection output, asillustrated in FIGS. 11A and 11B.

In view of such circumstances, the present invention envisages briningabout the following four major phases:

(A) The detection output from the acceleration sensor is analyzed todiscriminate whether the user's movement is walking or running.

(B) The detection output from the acceleration sensor is analyzed toobtain the tempos of the user's walking or running.

(C) Upon analysis in phase (B) above, analysis algorithms are changedbetween walking and running.

(D) The changing of the analysis algorithms in phase (C) above is basedon a discrimination output from phase (A) above.

(2) Discrimination Between Walking and Running

As shown in FIGS. 11A and 11B, the peaks in waveforms derived from thedetection output from the acceleration sensor differ significantlybetween walking and running in periodicity and amplitude. The waveformpatterns also differ appreciably between the two modes of physicalactivity. It is thus possible to discriminate whether the user'smovement is walking or running based on both the difference in terms ofperiodicity and amplitude of the waveform peaks stemming from theacceleration sensor detection output and the difference in waveformpatterns.

(2-1) Difference in Peak Periodicity

Generally, the speed of walking is 50 to 100 m/min and the speed ofrunning is 140 m/min or higher. The average human step is 70 cm for menand 65 cm for women.

It is therefore determined that the average man is walking if the numberof steps taken is fewer than 143 per minute and is running if the stepcount is 200 per minute or larger. Likewise it is determined that theaverage woman is walking if the number of steps taken is fewer than 153per minute and is running if the step count is 215 per minute or larger.

(2-2) Difference in Waveform Amplitude

The magnitude of the impact on the user's body from the user's physicalactivity is about 1.1 to 1.2 times the user's weight during walking andabout three to four times the body weight during running. The differencein impact between the two modes of activity is attributable to the factat least one of the user's feet is on the ground during walking whilethe user's both feet can be momentarily off the ground during running.It follows that walking and running can be distinguished from each otherby detecting the varying amplitude in waveforms derived from theacceleration sensor detection output.

(2-3) Difference in Waveform Pattern

The periodic waveform patterns derived from the acceleration sensordetection output prove to be distinctly different between walking andrunning when subjected to autocorrelation calculations. Performingautocorrelation calculations on the waveforms stemming from theacceleration sensor detection output allows noise and fluctuations to beremoved from the waveforms.

(2-4) How to Discriminate Between Walking and Running

According to an embodiment of the present invention, the techniquesoutlined in paragraphs (2-1) through (2-3) above are used todiscriminate between walking and running. The result from using each ofthe techniques is evaluated for further discrimination between walkingand running. Given the result of such discrimination, it is possible todetermine an optimal algorithm for acquiring the tempos of walking orrunning through analysis of the acceleration sensor detection output.

(3) Preferred Embodiments

One preferred embodiment of the present invention is a walking-supportaudio reproducing apparatus furnished with play lists. With the tempo ofthe user's walking detected, the audio reproducing apparatus mayreproduce songs from the play list that corresponds to the detectedwalking temp.

(3-1) Typical Structure of the Audio Reproducing Apparatus

FIG. 1 is a schematic flow diagram showing a typical structure of awalking-support audio reproducing apparatus 100 embodying the presentinvention. The audio reproducing apparatus 100 may be used either as awalking-support apparatus or as a general-purpose portable music player.Although not shown, the apparatus has a structure and a shape smallenough and compact enough to be carried around by the userillustratively in his or her pocket during walking.

The audio reproducing apparatus 100 has a system control circuit 10composed of a microcomputer. The control circuit 10 includes a CPU 11for executing programs, a ROM (read only memory) 12 that holds variousdata, a RAM (random access memory) 13 that provides a work area, and anonvolatile memory 14. The memories 12, 13 and 14 are connected to theCPU 11 via a system bus 19.

In the above setup, the nonvolatile memory 14 serves to retain diverseinformation about the audio reproducing apparatus 100 and its user. Thenonvolatile memory 14 is illustratively made up of a flash memory andcontains a conversion table such as one (CNVTBL) shown in FIG. 2.

The conversion table CNVTBL is used illustratively to convert the temposof the user's walking and of songs into tempo numbers TN. In theconversion table CNVTBL, the tempos of the user's walking and of songsare classified into seven categories represented by serial tempo numbersTN (=1 to 7), as shown in FIG. 2 (the categories are “0 to 69 bpm,” “70to 119 bpm,” . . . , “210 to 999 bpm” as indicated).

With the conversion table CNVTBL of FIG. 2 in use, a detected tempo willbe converted to TN=2 if the tempo falls into the range of, say, 70 to119 bpm, and to TN=3 if it falls illustratively into the range of 120 to139 bpm.

The nonvolatile memory 14 also contains play lists PL(1) through PL(7)as shown in FIG. 3. The play lists PL(1) through PL(7) have songsregistered therein by tempo. The numbers one through seven of the playlists correspond to the tempo numbers one through seven in theconversion table CNVTBL. The songs having the tempo applicable to agiven tempo number TN are registered in the play list PL(TN) of thecorresponding number.

More specifically, songs A1 through Aa with their tempos falling betweenzero and 69 bpm (TN=1) are registered in the play list PL(1); songs B1through Bb with their tempos between 70 and 119 bpm (TN=2) areregistered in the play list PL(2); and so on. Songs G1 through Gg withtheir tempos at or higher than 210 bpm (TN=7) are registered in the playlist PL(7).

The audio reproducing apparatus 100 also has a storage 21. The storage21 accumulates or stores music data and digital audio data to bereproduced as songs. For that purpose, the storage 21 is constituted bya large-capacity flash memory or by a small hard disk drive.Illustratively, the music data held in the storage 21 is digital audiodata compressed in MP3 (MPEG-1/Audio Layer 3, MPEG means Motion PictureExperts Group) format.

The storage 21 is connected to the system bus 19. A reproduction circuit22 is also connected to the system bus 19. The reproduction circuit 22is made up of a decoder circuit, a D/A (digital to analog) convertercircuit, and an output amplifier. The decoder circuit decompressescompressed music data back to the original audio data. The D/A convertercircuit converts the digital audio data into an analog audio signal.

Music data retrieved from the storage 21 is supplied to the reproductioncircuit 22. The reproduction circuit 22 decompresses the supplied musicdata and converts the decompressed data to an analog audio signal.Following the D/A conversion, the analog audio signal is output to aheadphone jack 23 that is connected with headphones 60.

An interface circuit 24 is also connected to the system bus 19. Musicdata is fed into the control circuit 10 from an externally furnishedpersonal computer 70 through an input connector 25 and the interfacecircuit 24 to be stored into the storage 21.

This embodiment of the invention is furnished with a three-dimensionalacceleration sensor 31 as a detection device that detects the walkingtempo of the user carrying the audio reproducing apparatus 100 around.The acceleration sensor 31 detects the motions, acceleration,vibrations, and swaying of the audio reproducing apparatus 100representative of the user's bodily movements (i.e., in terms ofacceleration). A detection output S31 from the acceleration sensor 31 isfed to a discrimination/analysis circuit 32.

The discrimination/analysis circuit 32, as will be discussed later inmore detail, analyzes the detection output S31 coming from theacceleration sensor 31 so as to detect the user's walk/run tempo. Uponanalysis, the discrimination/analysis circuit 32 discriminates betweenwalking and running using the procedure discussed in the paragraph (2)above in order to effect switchover to an optimal algorithm foranalyzing the walking or running.

Various operation keys are connected to the system bus 19. The systembus 19 is further connected with a display device such as an LCD (liquidcrystal display) 43 by way of a display control circuit 42. In thissetup, the operation keys are used illustratively to accomplish thefollowing: selecting the audio reproducing apparatus 100 either as ageneral-purpose portable music player or as a walking-support apparatus;selecting any one of different operation modes; selecting songs to play;and making other settings. The LCD 43 serves to display results of theoperation keys 41 having been operated and information about the songbeing reproduced.

(3-2) Operations

(3-2-1) Storing the Songs

The music data of a song desired to be stored into the audio reproducingapparatus 100 is prepared beforehand in compressed format on thepersonal computer 70. With the personal computer 70 connected to theaudio reproducing apparatus 100, a suitable transfer program is carriedout on the PC to designate transfer of the music data in question.

The music data prepared on the personal computer 70 is then supplied tothe audio reproducing apparatus 100 through the connector 25. Thesupplied music data is admitted into the audio reproducing apparatus 100through the interface circuit 24 under control of the CPU (centralprocessing unit) 11. The data is stored into the storage 21.

(3-2-2) Creating the Play Lists PL(1) Through PL(7)

Giving a command to create play lists causes the audio reproducingapparatus 100 to create skeleton play lists PL(1) through PL(7) (i.e.,play lists with no contents inside). The tempo of the song placed intothe storage 21 is analyzed using the procedure discussed in theparagraph (3-2-1) above. The analyzed tempo is converted to a temponumber TN by use of the conversion table CNVTBL. The analyzed song isregistered in the play list PL(TN) corresponding to the tempo numberresulting from the conversion from among the play lists PL(1) throughPL(7).

Illustratively, if an analysis of a given song reveals that it has atempo of 80 bpm, the tempo is converted by the conversion table CNVTBLinto TN=2. The song having that tempo is then registered in the playlist PL(2).

The tempo of a given song is acquired by performing a spectrum analysisof its music data and by obtaining an autocorrelation function of thedata. When the music data of a song is prepared on the personal computer70, information indicative of the tempo of that song may be added to themusic data as meta information that may later be used to identify thetempo. When the song is to be registered into any one of the play listsPL(1) through PL(7), the registration may be carried out using a filename of the corresponding music data together with the song title andthe name of the artist involved.

(3-2-3) Using the Embodiment as a General-Purpose Portable Music Player,for Music Reproduction

In this case, giving a command to reproduce a stored song causes theaudio reproducing apparatus 100 to retrieve the applicable music datafrom the storage 21. The retrieved music data is supplied to thereproduction circuit 22 for data decompression and digital-to-analogconversion.

The reproduction circuit 22 thus outputs an analog audio signal derivedfrom the retrieved music data. The analog audio signal is fed to theheadphones 60 allowing the user to listen to the reproduced song. Thetitle of the song being reproduced is displayed on the LCD 43.

Retrieval of music data from the storage 21 is controlled in accordancewith a currently established reproduction mode. That is, the retrievedmusic data may be subjected illustratively to single-song reproduction,all-song continuous reproduction, random reproduction, or repeatreproduction. In this manner, the audio reproducing apparatus 100 can beutilized as a general-purpose portable music player.

A command may also be given to designate one of the play lists PL(1)through PL(7) for reproduction. In such a case, only the songsregistered in the designated play list are reproduced selectively.Illustratively, when going to bed, the user might want to designate theplay list PL(1) to reproduce songs of slow tempos.

(3-2-4) Using the Embodiment as a Walking-Support Apparatus for MusicReproduction

In this case, the audio reproducing apparatus 100 is used to reproducesongs having tempos commensurate with the user's walking speed. Giving acommand to reproduce such songs causes the acceleration sensor 31 anddiscrimination/analysis circuit 32 to detect the tempo of the user'swalking. The walking tempo thus detected is converted by the conversiontable CNVTBL into a corresponding tempo number TN. Of the play listsPL(1) through PL(7), the play list PL(TN) corresponding to the temponumber TN derived from the conversion is selected. Then one of the songsregistered in the selected play list PL(TN) is selected.

The music data of the selected song is retrieved from the storage 21 andsent to the reproduction circuit 22 for data decompression anddigital-to-analog conversion. By the same procedure as that discussed inthe paragraph (3-2-3) above, the selected song is reproduced andlistened to by use of the headphones 60. Because the tempo of the songbeing reproduced is commensurate with the user's walking speed, the usercan walk rhythmically and pleasantly in time with the song.

During the walking, the current tempo number TN is compared with thepreceding tempo number TN. A difference detected in the comparisonbetween the two numbers indicates a change in the walking tempo. In thatcase, another play list PL(TN) corresponding to the current walkingtempo TN is selected and songs are reproduced selectively from the newlyselected play list PL(TN).

As will be discussed later, the analysis of the user's walking tempo bythe discrimination/analysis circuit 32 is supplemented by thedetermination of whether the user's current activity is walking orrunning. That is, when play lists or songs are to be selected by theabove-described procedure, the result of the determination of whetherthe user's motion comes from walking or running may be additionallytaken into consideration.

(4) Typical Structure of the Discrimination/Analysis Circuit 32

FIG. 4 is a schematic flow diagram showing a typical structure of thediscrimination/analysis circuit 32. As shown in FIG. 4, thediscrimination/analysis circuit 32 is made up of an analysis circuit 32Aand a discrimination circuit 32B. The detection output S31 from theacceleration sensor 31 is supplied to the analysis circuit 32A. Byanalyzing what is supplied using an appropriate analysis algorithm, theanalysis circuit 32A detects the tempo of the user's walking or running.An output from the analysis circuit 32A following the detection is fedto the control circuit 10 through the system bus 19.

The detection output S31 from the acceleration sensor 31 is alsosupplied to the discrimination circuit 32B. In this setup, thediscrimination circuit 32B is constituted by a period detection circuit321, an amplitude detection circuit 322, an autocorrelation circuit 323,and a determination circuit 324. The circuits 321 through 323 are eachdesigned to process the detection output S31 by a different method whendetecting the probability of the user's movement being either walking orrunning. The determination circuit 324 evaluates outputs S21 through S23coming from the circuits 321 through 323, thereby determining whetherthe user is walking or running.

Illustratively, the period detection circuit 321 subject the detectionoutput S31 from the acceleration circuit 31 to spectrum analysis inorder to detect periodicity of peaks (marked by small circles in FIG.11). On the basis of the periodicity thus detected, the period detectioncircuit 321 acquires the probability of the user either walking orrunning by use of the procedure discussed in the paragraph (2-1) above.The resulting detection output S21 from the period detection circuit 321is fed to the determination circuit 324.

The amplitude detection circuit 322 illustratively demodulates thedetection output S31 from the acceleration sensor 31 to detect theamplitude of the peaks (marked by small circles in FIG. 11) in theoutput S31. Based on the values of amplitude thus detected, theamplitude detection circuit 322 acquires the probability of the usereither walking or running by use of the procedure discussed above in theparagraph (2-2) above. The resulting detection output S22 from theamplitude detection circuit 322 is forwarded to the determinationcircuit 324.

The autocorrelation circuit 323 performs autocorrelation calculations onthe detection output S31 from the acceleration sensor 31 to obtain themagnitude of autocorrelation in the output S31. On the basis of themagnitude of autocorrelation thus acquired, the autocorrelation circuit323 detects the probability of the user either walking or running by useof the procedure discussed in the paragraph (2-3) above. The resultingdetection output S23 from the autocorrelation circuit 323 is sent to thedetermination circuit 324.

The determination circuit 324 evaluates the detection outputs S21through S23 coming from the circuits 321 through 323 respectively inorder to determine whether the user's activity is walking or running.The result of the determination is output as a discrimination output S24of the discrimination circuit 32B. Illustratively, if the detectionoutputs S21 through S23 each indicate the probability of the user'swalking or running in percentage points, these values are weightedbefore they are added up. The addition allows the determination circuit324 to determine whether the user is walking or running. If thedetection outputs S21 through S23 each indicate the probability ofwalking or running in binary form, the determination circuit 324 maydetermine whether the user is walking or running by a majority decisionderived from the outputs S21 through S23.

The discrimination output S24 from the discrimination circuit 32B issupplied as a control parameter to the analysis circuit 32A. Given thediscrimination output S24, the analysis circuit 32A switches accordinglyto a suitable algorithm for analyzing the detection output S31 from theacceleration sensor 31. The analysis algorithm derived from theswitchover is an optimal algorithm for analyzing the tempo of the user'swalking or running. In this setup, the discrimination output S24 is alsosupplied to the control circuit 10.

The user's walking or running is analyzed specifically by differentmethods as follows: in the waveform of the detection output S31 of FIG.11A observed during walking, near the peaks (marked by small circles)correctly representing the tempo of walking also appear other peaks thatcan lead to error. Since these peaks do not differ considerably inamplitude, they are first subjected to autocorrelation calculations.This process roughly determines the periodicity of the peaks. With thecoarse periodicity thus determined and with a given peak spotted, a timeframe is assumed in the probable position of the next peak, to see ifsuch a peak exists in the frame. If a plurality of peaks are found inthe time frame, the frame is narrowed so as to select a peak that isclose to a peak period. If no such peak is found in the time frame, theframe is widened in the search for a periodical peak. The periodicalpeak thus detected is stored temporarily as the basis for detecting thenext peak.

In the waveform of the detection output S31 of FIG. 11B observed duringrunning, the detected peaks are much more distinct in amplitude than thepeaks observed during walking. This makes it possible to handle only thewaveform peaks that exceed a predetermined threshold level. The processis implemented using a level comparator or a nonlinear amplifier. In thecase of FIG. 11B, the threshold level may be set illustratively for1,200. With the threshold determined, peaks exceeding it are observedand the interval between two adjacent peaks is regarded as a peakperiod. A search is then made for a waveform peak close to the nextperiod. The periodical peak thus detected is used also in this case asthe basis for detecting the next peak.

Many people are unconsciously in the habit of exerting a more force oneither foot than the other during walking or running. For that reason,it is preferred that the length of time for analysis using theabove-mentioned autocorrelation calculations include a peak period ofnot one step but two steps. When a difference is observed between theright and left feet in terms of the force exerted thereon, thischaracteristic may also be taken into consideration in the search forwaveform peaks representative of the tempo of walking.

The waveforms in FIGS. 11A and 11B vary depending on where theacceleration sensor 31 is installed, how the audio reproducing apparatus100 is attached or held, what type of shoes is worn by the user, or whatkind of condition the terrain or the floor is in on which to walk orrun. In view of these factors, the analysis methods discussed above maybe supplemented by such procedures as band-pass filtering and frequencyspectrum analysis for selective application of the parameters involvedto the analysis of walking or running.

Where the discrimination/analysis circuit 32 of FIG. 4 is in use, thedetection output S31 from the acceleration sensor 31 is analyzed asdescribed above for discrimination between walking and runningrepresentative of the user's movement. The output of the discriminationis used to change analysis algorithms for analyzing the tempo of walkingor running. This makes it possible to adopt an optimum algorithm foranalyzing the tempo of walking or running, whereby the probability oferror is lowered significantly.

(5) Walking Tempo

In the paragraphs that follow, the tempo of walking in general and atypical method for creating the conversion table CNVTBL will bediscussed.

(5-1) Observations

Fourteen test subjects (eight adult males and six adult females) wereobserved in their walking habits in daily life. The observationsrevealed that their walking movements could be roughly classified intofour groups: low-speed walking, normal walking, jogging, and dash asshown in FIG. 5. These four groups of walking may be applied byextension to the walking activity in general in everyday life.

The test subjects were also measured for their walking tempos. Theresulting measurements are shown graphically in FIG. 6. The horizontalaxis of FIG. 6 stands for walking tempos (i.e., average tempo of walkingper unit time) and the vertical axis denotes frequency (i.e., number ofpeople). In FIG. 6 and subsequent figures, the walking tempos are shownrounded to increments of 10 bpm.

The measurements above reveal that the walking tempos in daily life arenot uniformly distributed; they tend to be included in one of thegroups. It is also revealed that the walking tempos of less than 69 bpm,140 to 159 bpm, and 240 bpm and higher rarely occur in everyday life.For each group, it is possible to obtain the mean value, standarddeviation, and coefficient of variation of the tempos involved and toestimate their ranges.

People are thought to select automatically an optimally efficient stateof transport energy consumption when walking or running. The walkingtempos in the range of 140 to 159 bpm come between walking and joggingand fall into the state generally known as race walking. In daily life,people rarely, if ever, walk in the state of race walking. Hence theresulting measurements obtained as described above.

Each user has a particular pattern of walking as mentioned earlier. Theaudio reproducing apparatus 100 is arranged to learn its user's patternof walking. The results of such learning are then turned into theconversion table such as one (CNVTBL) shown in FIG. 2.

(5-2) Learning of Walking Tempos

For the purpose of learning, the user carries the audio reproducingapparatus 100 and takes a walk. During the walking, as shown in FIG. 7,the audio reproducing apparatus 100 measures instantaneous walkingtempos MT(t) at intervals of several milliseconds to several seconds.Mean walking tempos m_MT(t) at intervals of several seconds are thencalculated from the measured walking tempos MT(t). FIG. 7 shows resultsobtained when the audio reproducing apparatus 100 measured the walkingtempos MT(t) at intervals of one second and the measurements were usedas the basis for calculating the mean walking tempos m_MT(t) atintervals of five seconds.

The walking tempos m_MT(t) thus calculated are accumulated in thestorage 21 of the audio reproducing apparatus 100. This is how thereproducing apparatus 100 learns the user's walking tempos m_MT(t).

Once the walking tempos are learned, the audio reproducing apparatus 100is connected to the personal computer 70 as shown in FIG. 1. From theaudio reproducing apparatus 100, the accumulated walking tempos m_MT(t)and timestamp information are transferred to the personal computer 70.If the personal computer 70 currently retains any past walking temposm_MT(t) and timestamp information, they may be replaced by, or mergedwith, the newly transferred walking tempos m_MT(t) and timestampinformation.

(5-3) Division of Walking Tempos into Groups

The personal computer 70 creates a histogram of walking tempoappearances based on the transferred walking tempos m_MT(t) andtimestamp information. From the histogram, maximum values MD(i) max(i=1, 2, 3, . . . ) are detected and the detected values are taken asvertexes representing the walking tempos classified into groups MD(i).

FIG. 8 shows a typical histogram created from the walking temposm_MT(t). The horizontal axis of FIG. 8 stands for the walking temposm_MT(t) and the vertical axis denotes the number of walking tempoappearances. In this histogram, the maximum values are established asMD(1)max, MD(2)max, MD(3)max, MD(4)max, and MD(5)max on the horizontalaxis from left to right. These maximum values MD(n)max (n=1 to 5) aretaken as vertexes each topping one of the groups MD(n) in which thewalking tempos are distributed.

For each of the groups MD(n), a lower limit value MD(n)lower and anupper limit value MD(n)upper are obtained. If a given group MD(n) doesnot overlap with any other group, attention is paid to both ends of thegroup MD(n); the value on the horizontal axis at which the number ofappearances is zero is taken either as the lower limit value MD(n)loweror as the upper limit value MD(n) upper.

If two groups MD(n−1) and MD(n) overlap with each other, a median valuebetween the maximum value MD(n−1)max of the group MD(n−1) and themaximum value MD(n)max of the group MD(n) is regarded both as the upperlimit value MD(n−1)upper of the group MD(n−1) and as the lower limitvalue MD(n)lower of the group MD(n).

If the maximum value is positioned at the top or bottom end of thehistogram as in the case of the maximum value MD(5)max of the groupMD(5) in FIG. 8, that maximum value and the group associated with it areignored.

When the groups MD(n) are reorganized using the above-describedprocedure, it is possible to obtain four pairs of the lower limit valueMD(n)lower and upper limit value MD(n)upper (n=1 to 4) from thehistogram of FIG. 8, as indicated in FIG. 9A.

The values n=1, 2, 3, 4 are associated with the tempo numbers TN=2, 3,5, 6 respectively, as shown in the right-hand side column of FIG. 9A. Atthe same time, the ranges of walking tempos delimited by the lower limitvalue MD(TN)lower and upper limit value MD(TN)upper as designated bythese variables TN are registered in the conversion table CNVTBL, alongwith the correspondence between the ranges and the variables TN. Theregistrations lead to preparation of the lines indicated by the variableTN=2, 3, 5, 6 in the conversion table CNVTBL shown in FIG. 2.

Where the walking tempos m_MT(t) are less than 69 bpm (too slow),between 140 and 159 bpm (race walking), and higher than 210 bpm (toofast) in FIG. 8, they correspond to the groups MD(5), MD(6) and MD(7)(n=5, 6, 7) in FIG. 9B respectively.

The values n=5, 6, 7 are associated with the tempo numbers TN=1, 4, 7respectively, as shown in the right-hand side column of FIG. 9B. At thesame time, the ranges of walking tempos delimited by the lower limitvalue MD(TN)lower and upper limit value MD(TN)upper as designated bytheses variables TN are registered in the conversion table CNVTBL, alongwith the correspondence between the ranges and the variables TN. Theregistrations lead to preparation of the lines indicated by the variableTN=1, 4, 7 in the conversion table CNVTBL shown in FIG. 2. FIG. 10graphically summarizes the relationship between the ranges of walkingtempos on the one hand and the tempo numbers TN on the other handindicated in FIGS. 2, 9A and 9B.

The conversion table CNVTBL is thus created by the procedure discussedabove. The created conversion table is transferred from the personalcomputer 70 to the audio reproducing apparatus 100 wherein thetransferred table is retained illustratively in the memory 14.

(6) CONCLUSIONS

The above-described reproducing apparatus 100 analyzes the detectionoutput S31 from the acceleration sensor 31 to discriminate whether theuser's movement is walking or running, and changes analysis algorithmsfor detecting the tempos of the user's walking or running determined onthe basis of the discrimination output. This makes it possible to use anoptimal algorithm for analyzing the walking or running tempos andthereby to reduce errors significantly in the analysis.

Illustratively, the audio reproducing apparatus 100 creates the playlists PL(1) through PL(7) by walking tempo as shown in FIG. 3,discriminates which of the play lists PL(1) through PL(7) corresponds tothe currently detected walking tempo m_MT(t), and selectively reproducessongs from the play list thus discriminated. That is, whether thewalking tempo is slow or fast, the songs to be reproduced areautomatically changed to suit the user's current movement. The user hasa pleasant feeling that the reproducing apparatus 100 is selectivelyreproducing songs to match his or her physical activity at the presentmoment.

Because the play lists PL(1) through PL(7) have been acquired throughlearning, there is no need for the user to fine-tune the listed choicesor make additional adjustments to the lists. Furthermore, the listingsare affected very little by the user's physical conditions, variationsamong individual users, or fluctuations in a given user's walking.

(7) OTHERS

In the foregoing description, the embodiment of the invention was shownusing the seven play lists PL(1) through PL(7). Alternatively, there maybe prepared one play list of songs at tempos of 69 bpm or lower, 14 playlists covering songs at tempos between 70 and 209 bpm in increments of10 bpm, and one play list of songs at tempos of 210 bpm or higher. Anyof these play lists may be selected for reproduction of the songscontained inside in keeping with the detected tempo of walking orrunning. As another alternative, there may be prepared two play lists,one covering songs at tempos of 139 bpm or lower and the othercontaining songs at tempos of 140 bpm or higher. Either of the two playlists may then be selected for reproduction of the songs containedinside in keeping with the detected tempo of walking or running.

The personal computer 70 may create the play lists PL(1) through PL(7)and transfer the created lists to the audio reproducing apparatus 100together with the digital audio data constituting the songs held insidethe lists. It is also possible for the audio reproducing apparatus 100to have a standard conversion table CNVTBL installed therein beforehand.Every time the user takes a walk, the standard conversion table CNVTBLmay be corrected or adjusted to reflect the user's own walking pattern.In this case, the longer the audio reproducing apparatus 100 is used,the more accurate the selection of songs to be reproduced in accordancewith the user's unique walking pattern.

In the above-described example, the audio reproducing apparatus 100 wasdescribed as being hung from the user's neck by a neck strap.Alternatively, it might happen that the user wants to carry theapparatus around in a pocket of the clothes he or she wears or in a baghe or she carries. In such cases, appropriate analysis algorithms may bedevised to address the tempos of the user keeping the apparatus in hisor her pocket or bag while walking or running.

The discrimination/analysis circuit 32 may be implemented either byhardware such as a DSP (digital signal processor) or by software made upof programs performed by the CPU 11. Whenever any song to be reproducedis changed from the initial category, that change may be evaluated interms of how the operation keys 41 are operated. The evaluations maythen be used as the basis for subsequently selecting songs more to theuser's taste. It is also possible for the user of the audio reproducingapparatus 100 to establish conditions for changing songs or to set orvary the lower limit value MD(n)lower and upper limit value MD(n)upperby himself or herself by taking a look at the histogram of FIG. 6.

The acceleration sensor 31 may be separated from the audio reproducingapparatus 100 and attached to, say, the headphones 60. In this case, thedetection signal from the acceleration sensor 31 may be sent to thediscrimination/analysis circuit 32 in wired or wireless fashion. Theacceleration sensor 31 may be replaced by a speed sensor or by a gyrosensor. Furthermore, the music data may be integrated with video digitaldata.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factor in so far as they arewithin the scope of the appended claims or the equivalents thereof.

1. A content reproducing apparatus comprising: a sensor; adiscrimination circuit configured to discriminate whether a movement ofa user is a first movement or a second movement based on a detectionoutput from said sensor; a storage configured to store contents; areproduction circuit configured to reproduce said contents; and acontrol circuit configured to supply said reproduction circuit withcontents retrieved from said storage in accordance with a discriminationoutput from said discrimination circuit.
 2. The content reproducingapparatus according to claim 1, further comprising an analysis circuitconfigured to analyze tempos of said first movement or said secondmovement of said user in accordance with said detection output from saidsensor; wherein said analysis circuit changes analysis algorithms foranalyzing said tempos based on said discrimination output from saiddiscrimination circuit; and said control circuit retrieves contents fromsaid storage in accordance with the tempo analyzed by said analysiscircuit.
 3. The content reproducing apparatus according to claim 2,wherein, in accordance with said tempo analyzed by said analysiscircuit, said control circuit selects a predetermined play list from aplurality of play lists derived from said contents classified by apredetermined tempo, and retrieves applicable contents from said storagein accordance with the selected play list.
 4. The content reproducingapparatus according to claim 1, wherein, in accordance with saiddiscrimination output from said discrimination circuit, said controlcircuit selects a predetermined play list from a plurality of play listsderived from said contents classified by a predetermined tempo, andretrieves applicable contents from said storage in accordance with theselected play list.
 5. The content reproducing apparatus according toclaim 1, wherein said first movement and said second movement of saiduser are walking and running, respectively.
 6. The content reproducingapparatus according to claim 1, wherein said discrimination circuitincludes at least a period detection circuit configured to discriminatewhether said movement of said user is walking or running based onperiodicity of peaks in a waveform derived from said detection outputfrom said sensor.
 7. The content reproducing apparatus according toclaim 1, wherein said discrimination circuit includes at least anamplitude detection circuit configured to discriminate whether saidmovement of said user is walking or running based on amplitude of peaksin a waveform derived from said detection output from said sensor. 8.The content reproducing apparatus according to claim 1, wherein saiddiscrimination circuit includes at least an autocorrelation circuitconfigured to discriminate whether said movement of said user is walkingor running based on autocorrelation calculations of said detectionoutput from said sensor.
 9. The content reproducing apparatus accordingto claim 1, wherein said discrimination circuit includes: a plurality ofdetection circuits each configured to detect whether said movement ofsaid user is walking or running by use of one of algorithms differentfrom one another on the basis of said detection output from said sensor;and a determination circuit configured to determine whether saidmovement of said user is walking or running by evaluating detectionoutputs from said plurality of detection circuits and output the resultof the discrimination as said discrimination output.
 10. A contentreproducing method comprising the steps of: discriminating whether amovement of a user is a first movement or a second movement based on adetection output from a sensor; and supplying a reproduction circuitwith contents retrieved from a storage storing said contents inaccordance with a discrimination output from said discriminating step.11. The content reproducing method according to claim 10, furthercomprising the steps of: changing analysis algorithms for analyzingtempos of said first movement or said second movement of said user basedon said discrimination output from said discriminating step; andanalyzing said tempos of said first movement or said second movement ofsaid user by use of the analysis algorithm changed in said analysisalgorithm changing step.
 12. The content reproducing method according toclaim 11, wherein, in accordance with results from said analyzing step,said supplying step selects a predetermined play list from a pluralityof play lists derived from said contents classified by a predeterminedtempo, and retrieves applicable contents from said storage in accordancewith the selected play list.
 13. The content reproducing methodaccording to claim 10, in accordance with said discrimination outputfrom said discriminating step, said supplying step selects apredetermined play list from a plurality of play lists derived from saidcontents classified, and retrieves applicable contents from said storagein accordance with the selected play list.
 14. The content reproducingmethod according to claim 10, wherein said first movement and saidsecond movement of said user are walking and running, respectively. 15.The content reproducing method according to claim 10, wherein saiddiscriminating step includes at least discriminating whether saidmovement of said user is walking or running based on periodicity ofpeaks in a waveform derived from said detection output from said sensor.16. The content reproducing method according to claim 10, wherein saiddiscriminating step includes at least discriminating whether saidmovement of said user is walking or running based on amplitude of peaksin a waveform derived from said detection output from said sensor. 17.The content reproducing method according to claim 10, wherein saiddiscriminating step includes at least discriminating whether saidmovement of said user is walking or running based on autocorrelationcalculations of said detection output from said sensor.
 18. The contentreproducing method according to claim 10, wherein said discriminatingstep includes: a plurality of steps each arranged to detect whether saidmovement of said user is walking or running by use of one of algorithmsdifferent from one another on the basis of said detection output fromsaid sensor; and determining whether said movement of said user iswalking or running by evaluating detection outputs from said pluralityof detecting steps and output the result of the discrimination as saiddiscrimination output.
 19. A storage medium which stores acomputer-readable program for causing a computer to execute a procedurecomprising the steps of: discriminating whether a movement of a user isa first movement or a second movement based on a detection output from asensor; and supplying a reproduction circuit with contents retrievedfrom a storage storing said contents in accordance with a discriminationoutput from said discriminating step.